Stackable chair



FIG. 1 is a perspective view of a stackable chair showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a right side view thereof, the left side view being a mirror image thereof;

FIG. 5 is a top view thereof; and,

FIG. 6 is a bottom view thereof.

The broken lines illustrate portions of the stackable chair and form no part of the claimed design. 

The ornamental design for a stackable chair, as shown and described. 